Generator Help Needed

eystein

eystein

Well-known member
Assembled my 1930 Generator.

Have cleaned out everything, turned commutator changed bearings and replaced all broken insulation and re-soldered all connections.

Have successfully measured continuity and isolation of all parts after final assembly of the unit

When I connect the Generator to the battery, the generator turns like a motor at a moderate pace, drawing around 8-9 Amps unloaded. Ay idea of how fast it should should spin or how much current it should draw unloaded during this test ?

However, when I spin it up with an external motor it produces NO output.

Any suggestions as to what it can be ? I would think that if the problem was caused by bad windings it would not have run as a motor when connected to the battery.
 
Maybe be you re-polarized it when you ran your test? Try jumping the outputs briefly and try again. Make sure you are yurning in correct rotation?
 
Is this an early 1930 generator? The first few months the output stud was located at the front end of the case, and after April the stud was moved to the rear of the case. With the wire running to the front of the case, the factory taped it to the side of the field coil, and this makes it easier to mix it up with the field wire. I only mention this becasue I'm wondering if you are sure the adjustable brush is going to the field wire and not the output wire.

To check, just lift the adjustable brush off the commutator, or slip a piece of paper under that brush, then connect a battery charger to the adjustable brush and case. The battery charger should read about 4 amps on 6 volts. + to case.

I worked on a generator years ago that motored perfectly, but had no output. I changed the armature and it was fine.
 
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Would be good idea to check armature on a growler to see if it has an open circuit to one or more commutater bars,can even ground from armature to shaft.Was there any sign of thrown solder from the commutator? Tom has some good info too.
 
Sometimes when the commutator is turned down, some of the commutator metal will bridge the gaps between the segments. I always under cut the mica between the segments of the generator armature with a hacksaw blade. If the internal ground from the field coils is reversed the generator will motor backwards but will not charge. If the lead wire off the field coils is connected to the wrong brush, the generator will motor but will barely charge and adjusting the third brush will make no change.
 
The generator has been wired according to marking labels put on when I disassembled the generator. This also correspond to the attached drawing (found here on the barn) assuming that the view of the generator in that drawing is from the pulley end.

Have tried to polarize the generator by shorting it.

When motoring it turns clockwise.
 

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Tried running the generator with the field windings supplied with 6V from a battery charger, and the thing worked very well. However connecting the fields back on the third brush - nothing. The third brush will not give more than max 1 V to feed the fields, which obviously isn't enough.
 
There are two wires attached to the field coils. the wire with the largest end connector grounds to the generator housing. The small connector ended wire should connect to the third or adjustable brush. The terminal lead wire should connect to the insulated main brush. If the third or adjustable brush wire and the terminal lead wire that should connect to the insulated brush are reversed it will act just as you describe. The generator will barely charge and moveing the third brush will have no effect on the charge rate. Recheck your wire connections.
 
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Generator built after about March 1930 had the output stud moved to the rear of the case and had a large eyelet terminal for field ground and that fit under the insulating washer for the output stud. Generators built with the output stud towards the front of the case had a small eyelet terminal that mounted under a screw in the case for the field ground. In either case make sure you have the field wire connected tot he adjustable brush and make sure all 3 brush springs have good tension to push the brush into the commutator.

A generator with NO field hookup will put out about 1/2 volt from the residual magnetism in the field poles.

Do you have any closeup pictures of the brushes and field windings?
 
Tom and Purdy.

I hereby solemnly declare that the fields are hooked up to the adjustable third brush, and that the isolated fixed main brush is hooked up to the output terminal !!!!!!!

The other end of the fields is grounded at the screw on the grounded main brush.

Continuity and isolation of the assembly has been measured and found correct.

Connection has been verified from the commutator element under the brush up through the third brush and onto the terminal where the fields connect.

The third brush just wont give out the juice needed to drive the fields. Measured the voltage at the brush terminal to around 1V max.

The Growler man told me that the armature was OK. Is there any failure mode in which the armature can be verified OK on the growler, and perform its function of driving the generator output terminal, while not being able to feed the third brush ?
 
I can only make guesses at this point but here goes. You didn't say what parts had been replaced. Maybe the field coils need to be replaced. I have seen field coils that would show continuity through the leads but still wouldn't charge. Maybe the coils are grounding out. Did you replace the field coil insulators? When I check the armature with the growler, I first check with a hacksaw blade with the growler on for magnatism. If the hacksaw blade sticks to the armature, it is magnatised and will not charge. I then check each segment of the commutator for ground against the shaft of the armature. If any segment shows continuity between the segment and the armature shaft, this indicates that the segment is grounded and the armature should be replaced. The generator may still motor and barely charge with a grounded segment but should be replaced. I always replace the brush holder hardware such as the insulated washers and bushings. Any improper grounds or shorts at the brush holders caused by bad washers and insulator bushings will prevent the generator from charging. I may have already mentioned this but it is important to undercut the mica between the segments of the commutator on the armature. I use a hacksaw blade and cut the mica between each segment until the mica is slightly below the level of the segment. Sometimes or most times if the commutator is turned down in an armature lathe the gaps between the segments will be bridged. When the hacksaw blade is used to undercut the mica between the segments it will also correct any bridged condition between the segments. This pretty covers everything except a possible short at the terminal post. I always replace the terminal post components. I hope that some of this helps
 
Have you checked the field windings with a battery charger? I like to use my Sears 6 amp charger and connect the + clamp to the case then connect the - lead to the filed wire that goes to the adjustable brush. With the charger on 6 volts, you should have about a 3 to 4 amp draw on the common long generator.

Are the field coils installed correctly? If they have been removed, are they back in exactly the same way they came out? Just wondering why the field is grounded under the ground brush, rather than it's original ground spot, either under a small screw in the case, or under the output stud insulating washer?

One more thing to check is the connection where the two field coils are connected together. They should have the ends twisted and SOLDERED. I've seen a couple that were NOT soldered and had a poor connection, resulting in poor output.

Also make sure the long through bolts aren't touching and grounding any wires.
 
Tom Wesenberg said:
Also make sure the long through bolts aren't touching and grounding any wires.
Click to expand...

I've told this story before, but that is what happened to me. I was baffled because I knew everything was good. It was the third time opening the generator back up that I noticed that one bolt was was slipping OVER the insulator instead of under. Boy, did I feel stupid!!! Essentially one field was taken out of service as it was grounded between the two fields.

For what it's worth, I just checked the resistance on a couple sets of fields (probably NORS) and through both fields I got 1.1-1.2 ohms. Through one side only I averaged .7 ohms.
 
Tom,

everything that you mention has been done, and as I said, all elements have been measured for continuity and isolation after mounting. the only thing that might be is that I could have reversed the polarity of the fields, as i did not specificly mark each end of the fields while disassembling. anyway, I have connected the assembly according to the diagram shown earlier in the thread. In any case, I will check that. Please do not forget that the thing is outputting a 13-14V open circuit when the fields are supplied externally, but nothing when they are connected to the third brush.
 
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If the field coil wires are reversed, the generator will motor backwards. The generator is suppose to motor in the same direction that the engine turns when it is running. If the wires are reversed the generator will motor backwards but will not charge. I really don't think that this is the problem.
 
It motors clockwise when looking into the pulley from the front. So I guess that means that it cannot be reversed fields either.
 
If you have a 2011 Brattons catalog, Look on page 66 . There is a good exploded diagram of the generator and a good explaination about wire connections. My guess is ,if you have the wires properly connected, The problem is probably with the field coils.
 
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